Methods and Apparatus for Channel Occupancy Time (COT) Sharing in New Radio (NR) and/or Sidelink-Unlicensed (SL-U)

The present application relates to wireless communications systems and more particularly to methods and apparatus for supporting fair COT sharing, e.g., in NR-U and/or SL-U.

Some background will regard to New Radio-Unlicensed (NR-U) will now be described. A Channel Occupancy Time (COT) refers to the total time for which any gNB/UE(s) sharing the channel occupancy perform transmission(s) on a channel after it performs the corresponding channel access procedure described in 3rd Generation Partnership Project, Technical Specification Group Radio Access Network, specification titled Physical layer procedures for shared spectrum channel access which published as 3GPP TS 37.213 V18.1.0 (2023-12). This specification is hereby incorporated by reference in its entirety and will be hereinafter referred to as TS 37.213. A channel access procedure is a procedure based on sensing that evaluates the availability of a channel for performing transmissions. A gNB/UE may transmit a transmission using Type 1 channel access after first sensing the channel to be idle during the sensing durations of a defer duration and after a random back-off duration specified by channel access priority class (CAPC) in Table 4.1.1-1 of TS 37.213. Based on 3GPP NR-U specifications, a COT can be shared for transmission between a gNB and the corresponding UE(s). If a UE shares a channel occupancy initiated by a gNB, the UE may transmit a transmission that follows a DL transmission on scheduled resources after a gap as follows: i) if the gap is up to 16 μs, the UE can transmit the transmission on the channel after performing Type 2C channel access; ii) if the gap is 25 μs or 16 μs, the UE can transmit the transmission on the channel after performing Type 2A or Type 2B channel access procedures, respectively. COT Sharing information in NR-U will now be described.

COT sharing information can be configured by RRC (radio resource control) message and be exchanged between user equipment (UE) and gNB.

ChannelAccessPriority-r16 indicates the Channel Access Priority Class that the UE can assume when sharing the gNB initiated COT. Duration-r16/duration-r17 indicates the number of transmission slots within shared COT. Offset-r16/offset-r17 indicates the number of transmission slots from the end of the slot where the grant is detected after which COT sharing can be used.

Some background with regard to Sidelink-Unlicensed (SL-U) will now be described. Sidelink is a 3GPP access technology intended to provide direct connectivity between devices positioned inside or outside of a cell coverage area. SideLink has been gradually developed by 3GPP starting with Release 12 and continuing during the current Release 18. Sidelink unlicensed (SL-U) is operating in unlicensed/shared spectra in bands n46 and n96 (5 GHz and 6 GHz bands).

If a responding UE shares a channel occupancy initiated by a COT initiating UE using the channel access Type 1, the responding UE may transmit a SL transmission that follows a SL transmission by the COT initiating UE after a gap as follows.

If the gap is up to 16 μs and the transmission is limited to 584 μs, the responding UE can transmit the SL transmission on the channel after performing Type 2C SL channel access.

COT sharing information in Sidelink will now be described. It is also agreed in ongoing 3GPP Release 18 meetings to include the following information as part of COT sharing information.

A problem with regard to COT sharing in NR-U and SL-U, will now be described. In both NR-U and SL-U, the gNB or the initiator UE can share their obtained COT to another UE. The responding UE applies channel access type 2 (A/B/C) based on the gap between its transmission and the initiator's transmission to use the shared COT. In channel access type 2 (A/B), the responding UE is responsible to sense the channel for at least two or one sensing slot, respectively. However, with the channel access type 2 C, the responding U can start its transmission within a gap of 16 μs from the initiator's transmission without sensing the channel. Since the responding UE does not sense the channel in the channel access type 2 C, its transmission can interfere with transmission of other devices which are out the initiator's coverage (hidden to initiator) and operate on the same unlicensed bands. As a result, using a shared COT with channel access type 2 C can be unfair and problematic to other technologies operating on unlicensed bands such as IEEE 802.11 devices.

There is an out-of-sight node problem with regard to COT sharing in NR-U and SL-U. Here, we use the term, out-of-sight node to refer to the nodes that are out of the gNB/UE coverage and cannot sense that the channel is busy. The responding UEs who share the COT and perform Type C channel access might interrupt the transmission of out-of-sight nodes who did not sense the channel being busy.

illustrates an exemplary communications systemincluding a gNBwith a coverage areaand a plurality of UEs (UE 1, UE 2, UE 3, UE 4). UE 1and UE 3are currently located within coverage area, while UE 2and UE 4are currently located outside of coverage area.

In theexample, UE2and UE4are out-of-sight nodes with respect to gNBand cannot sense the channel being occupied by gNB. Consider that gNBdecides to share its COT with UE 1, as indicated by COT sharing informationbeing communicated from gNBto UE. Bi-directional arrowindicates communications between gNBand UE 1, which includes a downlink transmission from gNB1using a first portion of a shared COT, and an uplink transmission from UE 1to gNBusing a second portion of the shared COT. The uplink transmission from UE 1can potentially cause interference to other UEs within the area.

If UE1performs channel access 2C (with no sensing) to access the shared COT, initiated by gNB, it will interfere with transmissionof out-of-sight nodes, i.e., UE2and UE4.

includes a signaling diagramand corresponding legendused to illustrate the out-of sight node problem ofin more detail. Legendindicates that: widely spaced diagonal line shading is used to indicate type 1 CA and closely spaced diagonal line shading is used to indicate type 2-C CA with no sensing.

In this example gNBshares its COTwith UE 1. The gNBperforms type 1 CA, as indicated by block, followed by transmissionfrom gNB during the time interval T_0 to T_2 (to) of COT. During the time interval T_0 to T_2 (to) UE 1senses that the channel is busy, as indicated by dashed line block. Then, UE 1performs, e.g. based on a gap determination of less than 16 micro-sec, a Type 2-C channel access (CA) with no sensing, as indicated by block, and UE 1performs a transmission, using the remainder of the COT. UE 2, which is an out-of-side node, does not sense the transmissionby gNBon the channel. UE 2performs a type 1 channel access, which ends with a channel clear determination at time T_1. Then UE 2starts transmissionfrom UE 2directed to UE 4. As a result of the time overlap between transmissionand transmission, there is a collision at UE 4, as indicated by the encircled X. During the time interval T_0 to T_2 (to) UE 3senses that the channel is busy, as indicated by dashed line block. Then, UE 3performs a type 1 channel accessstarting at time T_2, which senses the channel to be busy and thus there is no transmission from UE 3, as indicated in information block.

To summarize, in the example, described with respect toand, assume gNBperforms Type 1 channel accessand occupies the channel at time T_0. The gNBuses a portion of its COTto transmit its own transmissionfrom T_0to T_2. During gNB transmission, UE 1and UE 3, which are within gNB's coverage, sense the channel to be busy (,) and refrain from transmission. However, UE 2, which is an out-of-sight node with respect to gNB, could perform Type 1 channel accessand start transmissionat T_1. Now, if UE 1performs Type 2C CA (with no sensing)at T_2and then uses the shared COT, its transmissionwill cause interference at UE 4, which is the destination of UE 2's transmission. Note that UE 3will refrain from transmission, when it performs CA type 1. The issue is not sensing the channel in CA 2C, performed by UE1.

Based on the above discussions, there is a need for new method and apparatus to reduce, eliminate, and/or mitigate interference to UEs, e.g., out-of-sight UEs, when COT is being shared in NR-U and/or SL-U.

Methods and apparatus for supporting fair COT sharing in NR-U and/or SL-U are described. Type 2C channel access (channel access without sensing) with regard to COT sharing for NR-U and/or SL-U is restricted based on the distance between an initiator device and a responding device. An initiator device determines a maximum distance threshold value, e.g., a COT-SharingRange2C value, and communicates the value to the responding UE as part of a generated set of COT sharing information. The responding UE receives the COT sharing information and recovers the maximum distance threshold value. The responding UE determines the distance (D) between the location of the initiating device and location of the responding UE. The responding UE compares the determined distance (D) to the maximum distance threshold value. If the comparison indicates that the determined distance D is less than the maximum distance threshold value, then the responding UE is allowed to perform a type 2C CA (without sensing) (e.g., for case where gap is less than 16 micro-seconds); otherwise, the responding UE performs a CA procedure which includes sensing, e.g. a type 2B CA procedure. If the responding UE is not able to determine its current location, e.g., to within a predetermined accuracy, the responding UE is not allowed to perform type 2C CA (without sensing) and uses a CA procedure which includes sensing. By restricting the type 2C CA for responding UEs with regard to COT sharing for NR-U and SL-U, in accordance with features of the present invention, the interference produced by responding UEs to out-of-sight UEs is reduced, mitigated, or eliminated, thus reducing collisions between responding UEs and out-of-sight UEs, and thus providing a fairer operational environment.

While various features are discussed in the above summary, all features discussed above need not be supported in all embodiments and numerous variations are possible. Additional features, details and embodiments are discussed in the detailed description which follows.

illustrates an exemplary communications systemincluding a base station, which is a gNB, with a coverage areaand a plurality of UEs (UE 1, UE 2, UE 3, UE 4). UE 1and UE 3are currently located within coverage area, while UE 2and UE 4are currently located outside of coverage area. In accordance with a feature of some embodiments of the present invention, distance-based COT sharing is used to minimize the effect of the out-of-sight node problem. Channel Access (CA) type 2C is only permitted to the UEs that are within a pre-specified distancefrom the gNB, e.g., located withing dashed line circle. In this way, the UEs that use the shared COT with CA 2C (with no sensing), will have minimized interference at out-of-sight nodes, i.e., UE4and UE2.

The interference to out-of-sight UEs, will approach to zero if the circle(representing coverage of the responding UE 1) is confined withing the larger circle(representing the coverage of the initiator gNB).

To limit the out-of-sight node problem, in accordance with a feature of an exemplary embodiment, the permitted distance(a maximum range) for performing Type 2C CA (for cases in which gap is less than 16 micro-seconds), is included in the COT sharing informationand is communicated from the initiator gNBto the responding UE, UE 1, with which the COT is being shared.

In some embodiments, a COT-SharingRange2C value is included in the COT sharing information, wherein said COT-SharingRange2C is referred to as the distance from the COT initiator in which accessing the shared COT with Type 2C CA is permitted by a responding UE.

For the responding UE, e.g. UE 1, to be able to calculate the distance from the initiator, in some embodiments, the location of the initiator, e.g., the location of gNB, is included in the COT sharing information, if not already included as Zone_id.

Using the information about its location and the location of initiator, included in the COT sharing information, the responding UE, e.g., UE 1, can calculate its distance to the initiator, e.g., gNB.

If the calculated distance is less than COT-SharingRange2C, the responding UE, e.g. UE 1, is permitted to use Type 2C CA (when gap is less than 16 micro-seconds), otherwise, it should use either Type 2A or 2B CA to access the shared COT.

is a drawing of an exemplary communications system, in accordance with an exemplary embodiment. Exemplary communications systemsupports NR-U and SL-U communications and supports exemplary methods for implementing fair COT sharing. Exemplary communications systemincludes a plurality of base station, e.g., gNBs, (base station 1, e.g., gNB 1, . . . , base station N, e.g. gNB N) and a plurality of UEs (UE 1, UE 2, UE 3, UE 4, UE 5, UE 6, UE 7, . . . , UE N). At least some of the UEs are mobile communications devices, which may move throughout the system. UE 1and UE 3are shown as being currently located within the wireless coverage areaof base station 1. UE 5and UE 6are shown as being currently located within the wireless coverage areaof base station N. UE 2, UE 4, UE 7and UE nare shown as being currently located outside of the cellular coverage areas,.

A base station, e.g., gNB 1, may, and sometimes does, share NR-U COT resources with a UE, e.g., UE 1, within its coverage area. In order to reduce or eliminate potential interference, e.g., collisions, with regard to UEs operating outside the cellular coverage area, methods and apparatus are implemented to limit the use of the type 2C channel access procedure with regard to responding UEs which are sharing COT resources granted by an initiating base station. In some embodiments, the determination as to whether a responding UE is allowed to perform type 2C channel access with regard to the COT sharing is based on whether or not the responding UE knows its location, e.g., to within an acceptable accuracy level, and the location of the responding UE with respect to a maximum distance threshold value from the base station which is initiating the COT sharing. For responding UEs located close to the initiating base station, type 2C channel access is permitted, while for responding UEs located far away from the initiating base station, e.g., near the outer boundaries of the cellular coverage area, type 2C channel access is not permitted with regard to the COT sharing. This conditional restriction of type 2C channel access, reduces, mitigates, or eliminates interference with respect to out-of-sight UEs, which are located outside the cellular coverage area.

Similarly, a UE, e.g., UE 2, may, and sometimes does, share SL-U COT resources with a UE, e.g., UE 4, within its coverage area. In order to reduce or eliminate potential interference, e.g., collisions, with regard to UEs operating outside the coverage area of UE 2, methods and apparatus are implemented to limit the use of the type 2C channel access procedure with regard to responding UEs which are sharing COT resources granted by an initiating UE. In some embodiments, the determination as to whether a responding UE is allowed to perform type 2C channel access with regard to the COT sharing is based on whether or not the responding UE knows its location, e.g., to within an acceptable accuracy level, and the location of the responding UE with respect to a maximum distance threshold value from the UE which is initiating the COT sharing. For responding UEs located close to the initiating UE, type 2C channel access is permitted, while for responding UEs located far away from the initiating UE, e.g., near the outer boundaries of the initiating UEs coverage area, type 2C channel access is not permitted with regard to the COT sharing. This conditional restriction of type 2C channel access, reduces, mitigates or eliminates interference with respect to out-of-sight UEs, which are located outside the coverage area of the initiating UE.

In some embodiments, the initiator device, e.g., initiator base station or initiator UE, with regard to the COT sharing determines and sends a maximum distance threshold value, e.g., a COT-SharingRange2C value, as part of the COT sharing information. In some such embodiments, the initiator device further includes information indicating the location of the initiator device or information, e.g., a device ID, which can be used by the responding UE to determine the location of the initiator device. The responding UE determines the distance between the initiator device and responding UE and uses the received maximum distance threshold value in making a decision as to whether or not the responding UE is permitted to use type 2C channel access procedure (with no sensing) with regard to its transmission using the granted shared COT resources.

The exemplary communications systemfurther includes network storage device, e.g., a server, which includes stored information, e.g., a table, mapping identifiers (e.g., BS IDs) of fixed location devices (e.g., fixed location base stations) to locations. The location mapping information in network storage devicemay be updated when a new base station is added to the system or activated. In addition, the location mapping information included in network storage devicemay be, and sometimes is, downloaded by UE devices to be available to determine a fixed location initiator device location for COT sharing, e.g. with regard to NR-U. The base stations (BS 1, . . . , BS N) are coupled together, to network storage device, to other network nodes including core network nodes, and/or to the Internet, via backhaul network, e.g., a network including wireline and/or fiber optic communications links. The UEs may be coupled to a base station via wireless communications links, e.g., using NR-U spectrum. The UEs may also be coupled to one another via wireless communications links, e.g., using SL-U spectrum.

, comprising the combination ofand, is a flowchartof an exemplary communications method in accordance with an exemplary embodiment. Operation starts in stepin which the communications system, e.g., communications systemof, is powered on and initialized. In some embodiments, operation proceeds from start stepto optional step. In other embodiments, operation proceeds from start stepto steps,,and, which may be performed in parallel.

Returning to step, in stepUEs, which may operate as responding UEs, with regard to COT sharing, are operated to store location information corresponding to one or more potential fixed location initiator devices, e.g., store a set of information mapping base station IDs to corresponding locations. Operation proceeds from stepto steps,,and, which may be performed in parallel.

In stepan initiator device (with regard to COT sharing), e.g. a base station (BS) such as a gNB, or a user equipment (UE), is operated to determine its location. Stepincludes stepor step. In stepthe initiator device, which is a base station, determines its location from stored configuration information. In stepthe initiator device, e.g., a base station or a UE, determines its location based on a GPS position fix. In some embodiments, the initiator device is a fixed location base station, and operation proceeds from stepto step, in which the fixed location base station stores its determined location and its BS ID, in a storage device, e.g., network storage device. In some embodiments, in the initiator device may change its location, and stepincluding stepis performed multiple times, e.g., with the current location of the initiator device being updated and stored in the initiator device.

In stepa responding UE is operated to determine its location. Stepincludes step, in which the responding UE determines its location based on a GPS position fix. In some embodiments, the responding device may, and sometimes does, utilize additional information, e.g., gyroscope and/or accelerometer measurements from an IMU included in the responding UE, to determine its location. The additional information is useful in determining a location when GPS signals are unavailable or degraded. Stepis performed repetitively, on an ongoing basis, and the determined current location is stored and/or updated within the responding UE.

In stepthe responding UE is operated to determine if the current determined location of the responding UE is known to within an acceptable threshold. In some embodiments, stepincludes step, in which the responding UE determines if the circular error probable (CEP), corresponding to determined location of step, is less than or equal to a predetermined validity threshold. In some embodiments, when the CEP is determined to be less than or equal to the validity threshold, the responding UE is considered to have obtained a valid position fix and is considered to know its location; otherwise, the position fix is considered to be a low accuracy position fix, and the responding UE is considered to not know its location. Although described in terms of CEP, other measures of accuracy e.g., R95 or 2 drms, may be, and sometimes are, used in determining whether or not the responding UE's location is known to within an acceptable validity threshold.

In stepan initiator device is operated to determine a maximum distance threshold value, e.g., a COT-sharing range_2C threshold value. Stepincludes step, in which the initiator device determines a maximum distance threshold value based on one or more or all of: energy threshold in energy detection (ED), channel propagation loss, and transmit power or the initiator device and responding UEs. Operation proceeds from stepto step.

In stepthe initiator device monitors for COT sharing opportunities. Stepis performed repetitively, on an ongoing basis. Stepmay, and sometime does, include step, in which the initiator device determines that there is a sharing opportunity, e.g., there are resources in a COT that will not be used by the initiator device. Operation proceeds from stepto step.

In stepthe initiator device generates COT sharing information. Stepincludes stepand step. In stepthe initiator device includes and configures variables in COT sharing information so the UEs (responding UEs) can determine their distance from the COT initiator. In some embodiments stepincludes stepor step. In stepthe initiator device includes information indicating the location of the initiator device in the COT sharing information. In some embodiments, the information indicating the location of the initiator device is included as a zone ID value. In step, the initiator device includes information, e.g., a base station (BS) identifier (ID) of the base station, which is the initiator device, from which the location of the initiator device can be determined, e.g., via using a BS ID to location mapping table, stored in the responding UE. In step, the initiator device includes the determined maximum distance threshold value, e.g., the determined COT-sharing range_2C threshold value, in the COT sharing information. Operation proceeds from stepto step.

In stepthe initiator device transmits the COT sharing information, e.g., in an information element (IE) ConfiguredGrant used to configure uplink transmission for NR-U or in Sidelink Control Information (SCI) carried on Physical Sidelink Control Channel (PSCCH) or Physical Sidelink Shared Channel (PSSCH) for SL-U. Operation proceeds from stepto step. SCI is normally carried in two phases, with the first phase communicating SCI in the PSCCH and the second phase communicating SCI in the PSSCH. Thus SCI can be communicated using either the PSCCH and/or the PSSCH. COT sharing information is mostly transported in 2nd phase of SCI using the PSSCH). Thus it should be appreciated that the COT sharing information can be, in accordance with the invention, communicated to a UE from an initiator device using either the PSCCH and/or the PSSCH. Which of the two channels or whether both channels are used depends on the particular embodiment but both channels are contemplated and one channel or both channels are used for communicating the COT sharing information generated in accordance with the invention with the particular channel used depending on the embodiment being implemented.

In stepthe responding UE receives the COT sharing information from the initiator device, said COT sharing information including the determined maximum distance sharing threshold and initiator device location information or information that can be used to derive the initiator device's location. Operation proceeds from stepto step.

In stepthe responding UE recovers the communicated maximum distance threshold value, e.g., the COT-sharing range_2C threshold value from the received COT sharing information. Operation proceeds from stepto step. In stepthe responding UE determines the initiator device location. Stepincludes stepsand. In stepthe responding UE recovers the communicated initiator device location or information, e.g., a BS ID, used to determine the initiator device location from the received COT sharing information. Operation proceeds from stepto step. In stepthe responding UE determines the initiator device location: i) to be the recovered initiator device location or ii) based on the recovered information used to determine the initiator device location and additional information, e.g., a stored mapping table mapping BS IDs to locations. Thus, in some embodiments, the responding UE determines the initiator device location directly from initiator device location information communicated in the COT sharing information. In some other embodiments, the responding UE determines the initiator device location based on information communicated in the COT sharing information in addition to additional information. For example, in some embodiments when the initiator device is a fixed location base station, the responding UE uses the recovered BS ID from the received COT sharing information and a BS ID to location mapping table, stored in the UE, to determine the initiator device location. Operation proceeds from step, via connecting node A, to step.

In stepthe responding UE determines a gap value, said gap value being a time between the end of the initiator device transmission and the intended start of the responding UE transmission on the COT, which is being shared, said gap value being one of: a value less than 16 micro-sec, 16 micro-sec, or 25 micro-sec, said gap being determined as a function of the responding UE device capabilities and current ongoing status, e.g. ongoing operation, of the responding UE. Operation proceeds from stepto step.

In stepthe responding UE determines if the gap is less than 16 micro-seconds. If the determination is that the gap is less than 16 micro-sec, as indicated by Y, then operation proceeds from stepto step. However, if the determination of stepis that the gap is not less than 16 micro-seconds, as indicated by N, then operation proceeds from stepto step.

Returning to step, in stepthe responding device determines whether or not the responding UE knows its location, e.g., to within a predetermined accuracy. If the determination is that that the responding UE knows its location, then operation proceeds from stepvia stepto step. If the determination is that that the responding UE does not know its location, then operation proceeds from stepvia stepto step.

In stepthe responding UE determines the distance (D) between the initiating device and the responding UE. Operation proceeds from stepto step.

In stepthe responding device makes a decision as to the type of channel access procedure (type 2C or type 2B) to use based on the determined distance (D) and the maximum distance threshold value, e.g., the COT-SharingRange2C value received in the COT sharing information. Stepincludes step,and. In stepthe responding UE compares the determined distance (D) to the maximum distance threshold value (e.g., the COT-SharingRange2C value). If the comparison of stepdetermines that the determined distance D is less than the maximum distance threshold value, then operation proceeds from stepto step, in which the responding UE decides to use a type 2C channel access procedure. Operation proceeds from stepto step. Alternatively, if the comparison of stepdetermines that the determined distance D is not less than the maximum distance threshold value, then operation proceeds from stepto step, in which the responding UE decides to use a type 2B channel access procedure. Operation proceeds from stepto step.

Returning to step, in step, the responding UE determines if the gap is 16 micro-sec or is 25 micro-sec. If the determination of stepis that the gap is 16 micro-seconds then operation proceeds from stepto step. Alternatively, if the determination of stepis that the gap is 25 micro-sec then operation proceeds from stepto step.

Returning to step, in stepthe responding UE is operated to perform a type 2C channel access procedure. Thus, the responding UE starts transmitting, using the granted COT resources, immediately after the determined gap without performing channel sensing. Operation proceeds from stepto step. In stepthe responding UE is operated to transmit signals, e.g., uplink signals or sidelink signals, using the shared granted COT resources.